Field
This disclosure is generally related to distribution of digital content. More specifically, this disclosure is related to a system and method for efficiently aggregating multiple interest messages for the same content from multiple predecessors.
Related Art
The proliferation of the Internet and e-commerce continues to create a vast amount of digital content. Content-centric network (CCN) architectures have been designed to facilitate accessing and processing such digital content. A CCN includes entities, or nodes, such as network clients, forwarders (e.g., routers), and content producers, which communicate with each other by sending interest packets for various content items and receiving content object packets in return. CCN interests and content objects are identified by their unique names, which are typically hierarchically structured variable length identifiers (HSVLI). An HSVLI can include contiguous name components ordered from a most general level to a most specific level. As an interest packet is routed through the network from a content requesting node to a content producing node, each intermediate CCN router adds an entry in its pending interest table (PIT) corresponding to the interest and forwards the interest to the next CCN router. When a matching content object packet is sent from the content producing node back to the requesting node, it follows the reverse path of the interest. Each intermediate CCN router forwards the content object along the requesting interfaces listed in the corresponding PIT entry and subsequently removes the PIT entry, indicating that the interest has been fulfilled.
An intermediate CCN node can receive multiple interests for the same content object (e.g., “similar interest”). A sending node can assign a lifetime for a similar interest based on an estimated round trip travel time for a packet. The intermediate node can receive an initial interest and add a corresponding entry in its PIT. Upon receiving a second or subsequent (“later”) similar interest, the intermediate node can aggregate the later interest in the same PIT entry as the initial interest by adding the requesting interface to the existing PIT entry and suppressing the forwarding of the later interest until after the expiration of the lifetime of the initial interest. As a result, an existing PIT entry with a long lifetime may block the forwarding of subsequent similar interests with a shorter lifetime, creating network inefficiency. In addition, interest lifetimes based on variable network metrics may not be reliable and can result in further network inefficiency. Therefore, what is needed is a PIT aggregation mechanism that does not block other requesters and does not require measurements of round trip travel time.